Recently, laminated vibrationproofing structures have been widely used as an vibration isolator for constructive structures (e.g. building). These laminated vibrationproofing structures are introduced between the structures and the foundation to decrease transmission of earthquake vibration energy to the structures. Wide variety of laminated vibrationproofing structures have been proposed. Normally, they are structures wherein a rigid plate and a large damping rubber layer having viscoelastic property are alternatively laminated (see FIG. 1 hereinafter).
Hitherto, in order to enhance a damping capacity, there have been proposed a method comprising formulating a large amount of carbon black or a filler in the rubber, or a method comprising adding a polymer having a high glass transition point. However, in these methods, elongation of the resulting rubber composition is lowered, or dependence of elastic modulus on temperature becomes large which results in excessive elastic modulus at the low temperature range of about -10.degree. C.
In the case of an earthquake, the laminated vibrationproofing structure produces vibrationproofing and damping effect by causing shear deformation and the larger the amount of shear deformation becomes, the better. Those which cause shear deformation of not less than 50% are desired. Although the laminated vibrationproofing structure is used at a temperature between about 30.degree. C. and -10.degree. C., it is important that the elastic modulus does not become too large on the low temperature side.
Further, the above damping effect is particularly effective for a rather strong earthquake which causes large deformation (e.g. shear deformation of not less than 5 %) in the laminated vibrationproofing structure. Accordingly, it is important that the laminated vibrationproofing structure has a large damping capacity at a large deformation range (e.g. not more than 5%). For that purpose, it is requested that Tan .delta. is large at the large deformation range.